Selective sintering of structurally modified polymers

ABSTRACT

A three-dimensional object is manufactured by selective sintering by means of electromagnetic radiation, wherein the powder comprises a polymer or copolymer having at least one of the following structural characteristics:
         (i) at least one branching group in the backbone chain of the polymer or copolymer, provided that in case of the use of polyaryletherketones (PAEK) the branching group is an aromatic structural unit in the backbone chain of the polymer or copolymer;   (ii) modification of at least one end group of the backbone chain of the polymer or copolymer;   (iii) at least one bulky group within the backbone chain of the polymer of copolymer, provided that in case of the use of polyaryletherketones (PAEK) the bulky group is not selected from the group consisting of phenylene, biphenylene, naphthalene and CH 2 — or isopropylidene-linked aromatics;   (iv) at least one aromatic group non-linearly linking the backbone chain.

FIELD OF THE INVENTION

The present invention relates to a process for manufacturing athree-dimensional object from a powder by selective sintering by meansof electromagnetic radiation, wherein the powder comprises a polymer orcopolymer. Furthermore, the present invention relates to athree-dimensional object manufactured by said process, an apparatus formanufacturing a three-dimensional object by means of said process andthe use of a preselected polymer powder in said process.

As for example known from DE 44 10 046, a process for manufacturing athree-dimensional object by selective sintering by means ofelectromagnetic radiation may be carried out layer-wise by means of asource for electromagnetic radiation. In such a process, athree-dimensional object is manufactured layer-wise by applying layersof powder and bonding these layers to each other by selectivesolidification of the powder at positions corresponding tocross-sections of the object.

DESCRIPTION OF BACKGROUND ART

FIG. 1 exemplary shows a laser sintering device by means of which aprocess for layer-wise manufacturing of a three-dimensional object maybe performed. As is apparent from FIG. 1, the device comprises acontainer 1. This container is open to the top and is limited at thebottom by a support 4 for supporting an object 3 to be formed. By theupper edge 2 of the container (or by its sidewalls) a work plane 6 isdefined. The object is located on the top side of the support 4 and isformed from a plurality of layers of a building material in powder formwhich is solidifiable by means of electromagnetic radiation, wherein thelayers are in parallel to the top side of the support 4. Thereby, thesupport is moveable in a vertical direction, i.e. in parallel to thesidewall of the container 1 via a height adjustment device. Therewith,the position of the support 4 can be adjusted relatively to the workplane 6.

Above the container 1, or rather the work plane 6, an application device10 is provided for applying the powder material 11 to be solidified ontothe support surface 5 or a previously solidified layer. Also, anirradiation device in the form of a laser 7, which emits a directedlight beam 8, is arranged above the work plane 6. This light beam 8 isdirected as deflected beam 8′ towards the work plane 6 by a deflectiondevice 9 such as a rotating mirror. A control unit 40 allows to controlthe support 4, the application device 10 and the deflection device 9.The items 1 to 6, 10 and 11 are located within the machine frame 100.

In the manufacturing of the three-dimensional object 3, the powdermaterial 11 is applied layer-wise onto the support 4 or a previouslysolidified layer and is solidified at the positions of each powder layercorresponding to the object by means of the laser beam 8′. After eachselective solidification of a layer, the support is lowered by thethickness of the powder layer to be subsequently applied.

Many modifications of processes and devices for manufacturing athree-dimensional object by selective sintering by means ofelectromagnetic radiation compared to the system described above exist,which can also be used. For example, instead of using a laser and/or alight beam, other systems to selectively deliver electromagneticradiation could be used, such as, e.g., mask exposure systems or thelike.

However, in previous processes for selective sintering by means ofelectromagnetic radiation of polymer powders, insufficient attention waspaid to the mechanical properties of the manufactured object.

OBJECT OF THE INVENTION

Therefore, the object of the present invention is to provide animprovement of a process for manufacturing a three-dimensional object byselective sintering by means of electromagnetic radiation of polymerpowders, which results in improved mechanical properties of themanufactured objects.

SUMMARY OF THE INVENTION

Various aspects, advantageous features and preferred embodiments of thepresent invention as summarized in the following items, respectivelyalone or in combination, contribute to solving the object of theinvention:

(1) A process for manufacturing a three-dimensional object from a powderby selective sintering by means of electromagnetic radiation, whereinthe powder comprises a polymer or copolymer which has at least one ofthe following structural characteristics:

-   -   (i) at least one branching group in the backbone chain of the        polymer or copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the branching group is an aromatic        structural unit in the backbone chain of the polymer or        copolymer;    -   (ii) modification of at least one end group of the backbone        chain of the polymer or copolymer;    -   (iii) at least one bulky group in the backbone chain of the        polymer of copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the bulky group is not selected from        the group consisting of phenylene, biphenylene, naphthalene and        CH₂— or isopropylidene-linked aromatics;    -   (iv) at least one aromatic group non-linearly linking the        backbone chain.        (2) The process according to item (1), wherein successive layers        of the object to be formed from solidifiable powder material are        subsequently solidified at positions corresponding to the cross        section of the object.        (3) The process according to item (1) or (2), in which process        the electromagnetic radiation is provided by a laser.        (4) The process according to any one of the preceding items,        which comprises a predefined and/or controlled cooling step        after the sintering step.        (5) The process according to item (4), which comprises a step of        cooling the object after completion of the object from a        temperature being 1-50° C., preferably 1-30° C. and more        preferably 1-10° C. lower than T_(m) of the polymer or copolymer        comprised in the powder, to T_(G) of the polymer or copolymer        comprised in the powder, at a cooling rate of 0.01-10° C./min,        preferably 0.1-5° C./min and more preferably 1-5° C./min,        wherein T_(m) is the melting point and T_(G) is the glass        transition temperature of the polymer or the copolymer comprised        in the powder.        (6) The process according to any one of the preceding items,        wherein the powder comprises a polymer or copolymer having a        melting point T_(m) in a range of 100° C. to 450° C., preferably        150° C. to 400° C. and more preferably 250° C. to 400° C.        (7) The process according to any one of the preceding items,        wherein the powder comprises a polymer or a copolymer, having a        glass transition temperature T_(G) in a range of 50 to 300° C.,        preferably 100° C. to 300° C. and more preferably 130 to 250° C.        (8) The process according to any one of the preceding items,        wherein the polymer or copolymer has a number average M_(n) of        at least 10,000, more preferably 15,000 to 200,000 and in        particular 15,000 to 100,000 or a weight average M_(w) of at        least 20,000, and more preferably 30,000 to 500,000 and in        particular M_(w) 30,000 to 200,000.        (9) The process according to any one of the preceding items,        wherein the polymer or copolymer has a polymerization degree n        of 10 to 10,000, more preferably 20 to 5000 and in particular 50        to 1000.        (10) The process according to any one of the preceding items,        wherein the polymer or copolymer contains at least one aromatic        group in the backbone chain, preferably in the repeating unit of        the backbone chain.        (11) The process according to any one of the preceding items,        wherein according to modification (iv) at least one non-linear        linking aromatic group is contained in the repeating unit of the        backbone chain.        (12) The process according to item (11), wherein according to        modification (iv) the non-linear linking aromatic groups are        independently selected from the group of 1,2- and 1,3-phenylene,        1,3-xylylene, 2,4′- and 3,4′-biphenylene, and 2,3- and        2,7-naphthalene.        (13) The process according to item (11) or (12), wherein        according to modification (iv) the polymer or copolymer contains        at least one additional, linear-linking aromatic group which is        different from the non-linearly linking aromatic group and/or at        least one branching group, in the backbone chain, preferably in        the repeating unit of the backbone chain.        (14) The process according to any one of the preceding items,        wherein the aromatic groups are independently from each other        selected from unsubstituted or substituted, monocyclic or        polycyclic aromatic hydrocarbons.        (15) The process according to item (13) or (14), wherein        according to modification (iv) the linear linking aromatic        groups are independently from each other selected from the group        consisting of 1,4-phenylene, 4,4′-biphenylene,        4,4′-isopropylidene diphenylene, 4,4′-diphenylsulfone, 1,4-,        1,5-, 2,6-naphtalene, 4,4″-p-terphenylene and        2,2-bis-(4-phenylen)-propane.        (16) The process according to any one of the preceding items,        wherein according to modification (i) the branching group is an        aliphatic hydrocarbon, an aromatic hydrocarbon or a heteroarene        which has at least one substituent or one side chain, in case of        the use of polyaryletherketones (PAEK), the branching group is        an aromatic structural unit in the backbone chain of the polymer        or copolymer.        (17) The process according to item (16), wherein according to        modification (i) the side chains independently from each other        are selected from the group consisting of C1 to C6 unbranched or        branched, chain- or ringshaped alkyl- or alkoxy groups and aryl        groups.        (18) The process according to item (16) or (17), wherein        according to modification (i) the side chains independently from        each other are selected from the group consisting of methyl,        isopropyl, tert-butyl or phenyl.        (19) The process according to any one of the preceding items,        wherein according to modification (ii) the end groups of the        backbone chain are modified by terminal alkyl, alkoxy, ester        and/or aryl groups.        (20) The process according to any one of the preceding items,        wherein according to modification (iii) the bulky group is an        aromatic or non-aromatic group, in case of the use of        polyaryletherketones (PAEK), the bulky group is not selected        from the group consisting of phenylene, biphenylene, naphthalene        and CH₂— or isopropylidene-linked aromatics.        (21) The process according to item (20), wherein according to        modification (iii) the bulky group is a polycyclic aromatic or        non-aromatic group.        (22) The process according to items (20) or (21), wherein        according to modification (iii) the bulky group is selected from        phenylene, naphthalene, anthracene, biphenyl, fluorenes,        terphenyl, decaline or norbornane.        (23) The process according to any one of the preceding items,        wherein a mixture of at least two different polymers or        copolymers is used, wherein at least one of the admixed        (co-)polymer components has at least one of the structural        characteristics mentioned in item 1.        (24) The process according to any one of the preceding items,        wherein the polymer or copolymer is formed on the basis of        polyamide (PA), polyaryletherketone (PAEK), polyarylethersulfone        (PAES), polyester, polyether, polyolefines, polystyrene,        polyphenylenesulfide, polyvinylidenefluoride,        polyphenyleneoxide, polyimide or a block copolymer that        comprises at least one of the aforementioned polymers.        (25) The process to any one of the preceding items, wherein the        polymer or copolymer is formed on the basis of polyamide (PA),        polyaryletherketone (PAEK), polyarylethersulfone (PAES) or a        block copolymer comprising at least one of the aforementioned        polymers.        (26) The process according to item (24) or (25), wherein the        block copolymer is preferably a polyaryletherketone        (PAEK)/polyarylethersulfone (PAES)-diblock copolymer or a        PAEK/PAES/PAEK-triblock copolymer.        (27) The process according to any one of the preceding items,        wherein the polymer is a polyaryletherketone (PAEK) formed on        the basis of polyetheretherketone (PEEK), polyetherketoneketone        (PEKK), polyetherketone (PEK), polyetheretherketoneketone        (PEEKK), polyetherketoneetherketoneketone (PEKEKK),        polyaryletheretheretherketone (PEEEK) or a copolymer comprising        at least one of the aforementioned polymers.        (28) The process according to item (27), wherein the        polyaryletherketone (PAEK) is formed on the basis of a        polyetherketoneketone (PEKK) polymer or copolymer.        (29) The process according to any one of the preceding items,        wherein the polymer or copolymer on the basis of        polyaryletherketone (PAEK) has a melting viscosity of 0.05-1.0        kN*s/m², preferably 0.15-0.6 kN*s/m² and in particular of        0.2-0.45 kN*s/m².        (30) The process according to any one of items (24) to (29),        wherein the polyaryletherketone (PAEK) polymer or copolymer has        a polymerization degree n of preferably 10 to 1,000, more        preferably 20 to 500, and in particular 40 to 250.        (31) The process according to any one of the items (27) to (30),        wherein the polyetherketoneketone (PEKK) polymer or copolymer        comprises 1,4-phenylene as the linear-linking aromatic group and        1,3-phenylene as the non-linear linking aromatic group in the        backbone chain of the polymer, preferably in the repeating unit        of the backbone chain.        (32) The process according to any one of the items (27) to (31),        wherein the ratio of repeating units comprising, respectively,        at least one 1,4-phenylene unit to repeating units comprising,        respectively, one 1,3-phenylene unit is 90/10-10/90, preferably        70/30-10/90, more preferably 60/40 to 10/90.        (33) A three-dimensional object obtained by a selective        sintering of a polymer, a copolymer or a blend of polymers in        powder form by means of electromagnetic radiation, wherein the        polymer or copolymer used for the powder has at least one of the        following structural characteristics:    -   (i) at least one branching group in the backbone chain of the        polymer or copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the branching group is an aromatic        structural unit in the backbone chain of the polymer or        copolymer;    -   (ii) modification of at least one end group of the backbone        chain of the polymer or copolymer;    -   (iii) at least one bulky group in the backbone chain of the        polymer of copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the bulky group is not selected from        the group consisting of phenylene, biphenylene, naphthalene and        CH₂— or isopropylidene-linked aromatics;    -   (iv) at least one aromatic group non-linearly linking the        backbone chain.        (34) The three-dimensional object according to item (33),        wherein the polymer or copolymer is defined as denoted in the        items 6 to 32.        (35) An apparatus for manufacturing a three-dimensional object        from a powder by selective sintering by means of electromagnetic        radiation of the powder, wherein said apparatus comprises a        temperature control device arranged for setting a predefined        cooling of the object after completion of manufacturing the        object.        (36) The apparatus according to item (35), wherein the cooling        rate set by means of the temperature control device depends on        the type of polymer, copolymer or polymer blend comprised in the        powder.        (37) The apparatus according to item (35) or (36), wherein the        temperature control device is set depending on the predetermined        type of polymer, copolymer or polymer blend.        (38) A manufacturing system including an apparatus according to        any one of items (35) to (37) and a powder comprising at least        one polymer or copolymer as defined in items (6) to (32).        (39) A use of a polymer powder in the manufacture of a        three-dimensional object by means of selective electromagnetic        irradiation sintering, wherein the polymer is preselected from a        polymer or copolymer having at least one of the following        structural characteristics:    -   (i) at least one branching group in the backbone chain of the        polymer or copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the branching group is an aromatic        structural unit in the backbone chain of the polymer or        copolymer;    -   (ii) modification of at least one end group of the backbone        chain of the polymer or copolymer;    -   (iii) at least one bulky group in the backbone chain of the        polymer of copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the bulky group is not selected from        the group consisting of phenylene, biphenylene, naphthalene and        CH₂— or isopropylidene-linked aromatics;    -   (iv) at least one aromatic group non-linearly linking the        backbone chain.        (40) The use according to item (39), wherein the polymer or        copolymer is defined as in items (6) to (32).

It has been surprisingly found that when structurally special modifiedpolymers or copolymers are applied in a selective sintering process, amarked improvement of certain, very advantageous mechanical propertiesincluding, but not limited to high stiffness, high compression strength,high impact strength, high maximal tensile- and bending strength as wellas high elongation at break and high heat deflection temperature areobtained in the manufactured three-dimensional objects, while on theother hand opposing characteristics such as good chemical resistance andlow post crystallisation are nevertheless well balanced. Furthermore, ithas been surprisingly found that by particular process conditions, or byobserving the cooling rate after sintering, respectively, provide forsignificant improvements of the aforementioned mechanical properties anda good balance with the opposing characteristics. Moreover, a markedlyimproved combination of both, appropriately set crystallinity and lowporosity in the manufactured three-dimensional object can be achieved,which contributes to a further improvement of the above mentionedproperties. The advantages of the invention are particularly feasiblewhen modified polyaryletherketone polymers or polyaryletherketonecopolymers or polyamide polymers or polyamide copolymers respectivelyare used as polymer material of the polymer powder. The advantageouscombinations of characteristics realized by the present invention aremainly attributed to the fact that the structurally special modifiedpolymers and copolymers enable the setting of an advantageous range ofcrystallinity in the manufactured three-dimensional object at coexistentlow porosity. Furthermore, the advantages of the invention are alsofeasible for composites, wherein the value of crystallinity relates tothe polymer matrix of the composite. Such composites comprise one ormore fillers and/or additives besides of a matrix of the respectivepolymer, copolymer or polymer blend.

For polymers in general, the final crystallinity in the obtained objectis 80% or less, preferably 50% or less, more preferably 5-70%, even morepreferably 15-50% and in particular 15-35%. Especially forpolyaryletherketones (PAEK), for example, the final crystallinity in theobtained object is 5 to 45%, preferably 10 to 40%, more preferably 15 to35%, even more preferably 15 to 30%, and in particular 20 to 25%.Especially for polyamides (PA), for example, the final crystallinity inthe obtained object is 10 to 50%, preferably 15 to 40%, more preferably15 to 35% and in particular 20 to 30%. The porosity for polymers ingeneral is less than 10%, preferably 5%, more preferably 3% and inparticular less than 2%.

As a preferred alternative to classical polymer processing technologiesinvolving pressure processing of polymers, like e.g. injection molding,the process according to the present invention can be carried outlayer-wise in an additive process, wherein successive layers of theobject to be formed from solidifiable powder material are subsequentlysolidified by the electromagnetic radiation at positions correspondingto the cross-section of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 exemplary shows a laser sintering device for a layer-wisemanufacturing of a three-dimensional object.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is now described in more detail by referring tofurther preferred and further advantageous embodiments and examples,which are however presented for illustrative purposes only and shall notbe understood as limiting the scope of the present invention.

In case the polymer powder material comprises a polymer or copolymerhaving at least one, optionally a combination of conditions selectedfrom the group consisting of (i) at least one branching group in thebackbone chain, (ii) a modification of terminal groups, (iii) at leastone bulky group, and (iv) at least one aromatic group non-linearlylinking the backbone chain, this can result in a marked improvement ofcertain, very advantageous mechanical-properties including highstiffness, high compression strength, high impact strength, high maximumtensile- and flexural-strength as well as high elongation at break andhigh heat distortion, while on the other hand opposing properties suchas good chemical resistance and low after-shrinkage bypost-crystallisation are nevertheless well balanced. Furthermore, adecrease of the porosity of the manufactured object can be made possibleadditionally contributing to the improvement of the mechanicalproperties of the manufactured object.

Objects manufactured by selective sintering by means of electromagneticradiation of a powder comprising at least one polymer typically have avalue of crystallinity substantially higher crystallinity than objectsmanufactured by classical polymer processing technologies like e.g.injection molding. That is, in a process for manufacturing athree-dimensional object from a powder by selective sintering by meansof electromagnetic radiation of the powder comprising at least onepolymer, for example of a type as it is illustrated in FIG. 1, thecrystallinity of the manufactured object tends to become high if nostructurally modified polymer or copolymer according to the invention isused. Specifically, in the layer-wise building process, a high powderbed temperature lying at about 1-50° C., preferably 1-30° C., even morepreferably 1-20° C. and most preferably 1-10° C. below the melting pointT_(m) of the polymer is generally used. The object is typically exposedto relatively high processing temperatures for a substantial period oftime and usually still undergoes very long cooling periods. To preventor minimize curling of the object during the building process, theprocessing temperature should be kept close to the melting point of thepolymer contained in the powder in order to provide for a goodconnection between successive layers and to minimize the formation ofpores due to an inadequately melting of the powder particles.Consequently, during the whole building process, the temperature of thepowder bed is kept above the crystallization temperature T_(c) of thepolymer. The formed object itself may be exposed for a long time totemperatures above T_(c). At the end of the building process, when allheating sources of the sintering machine are switched off, the coolingthrough T_(c) of the object starts due to natural heat loss to theenvironment. Because of the low heat conductivity of the polymer powderand the large powder bed, this may take hours to days, depending on thepolymer powder used and the processing conditions, i.e. withoutpredefining a proper cooling rate—which would possibly further increasecrystallization of the polymer object, eventually during the coolingprocess. Without proper control, even post-crystallization of the lasersintered polymer object may occur. As a consequence, relatively high andpartly extremely high crystallinities are obtained in the manufacturedobject without the controlled cooling step according to the presentinvention. In turn, without properly limiting crystallinity, relevantmechanical properties of the object may be deteriorated.

On the other hand, in the selective sintering process according to thepresent invention, the crystallinity in the manufactured object may bebeneficially adjusted still high enough to also provide for positiveinfluences on high chemical resistance, low post shrinkage attemperatures above T_(g) or high stiffness of the manufactured object.Thus, an excellent balance of properties can be achieved by the presentinvention.

When the crystallinity of the material manufactured from polymer powdermaterial is properly limited and preferably adjusted within a particularrange, a marked improvement of certain, very advantageous mechanicalproperties like tensile strength, Young's modulus and elongation atbreak can be attained. Particularly effective and preferred means inorder to limit the crystallinity of the manufactured object are: 1)Preselecting a suitable type of polymer material, 2) paying attention tothe structural characteristics and/or modifications of the polymercomprised by the preselected powder, and/or 3) paying attention to apredefined and/or controlled cooling step after completion of thesintering process of the object.

Thus, according to a preferred embodiment of the invention, a predefinedand/or controlled cooling step is preferably applied to the object aftercompletion of the object after the sintering. The predefined and/orcontrolled cooling step may be realized by predefined slow cooling,possibly slower than native (passive) cooling, or by active cooling inorder to provide fast cooling. As the conditions of the predefinedand/or controlled cooling step mainly depend on the type andspecification of the polymer, copolymer or polymer blend used, usefulsettings for said cooling step can be experimentally tested with theproviso that the final crystallinity in the manufactured object iscontrolled such that the manufactured object has the desired mechanicalcharacteristics.

However, the cooling rate after completion of the object may also affectthe curling and thus the dimensional stability of the object. It hasbeen surprisingly found that the cooling rate can be predefined suchthat the three-dimensional object has not only a decreased crystallinityproviding the above mentioned advantageous mechanical properties, butalso a high dimensional stability, that is, it does not curl.

A suitable type of polymer material can be selected frompolyaryletherketone (PAEK), polyarylethersulfone (PAES), polyamides,polyesters, polyethers, polyolefines, polystyrenes,polyphenylensulfides, polyvinylidenfluorides, polyphenylenoxides,polyimides and copolymers comprising at least one of the aforementionedpolymers, wherein the selection is however not limited to the abovementioned polymers and copolymers. For example, suitable PAEK polymersand copolymers are preferably selected from polyetheretherketone (PEEK),polyetherketoneketone (PEKK), polyetherketone (PEK),polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone(PEKEKK), polyaryletheretheretherketone (PEEEK) and copolymerscomprising at least one of the aforementioned polymers. Suitablepolyamide polymers or copolymers can be selected from the groupconsisting of polyamide PA6T/6I, poly-m-xylylenadipamide (PA MXD6),polamide 6/6T, polyamide elastomers like polyetherblockamide such asPEBAX™-based materials, polyamide 6, polyamide 66, polyamide 11,polyamide 12, polyamide 612, polyamide 610, polyamide 1010, polyamide1212, polyamide PA6T/66, PA4T/46 and copolymers comprising at least oneof the aforementioned polymers. Suitable polyesterpolymers or copolymerscan be selected from the group consisting of polyalkylenterephthalates(e.g. PET, PBT) and their copolymers with isophthalic acid and/or1,4-cyclohexanedimethylole. Suitable polyolefine polymers or copolymerscan be selected from the group consisting of polyethylene andpolypropylene. Suitable polystyrene polymers or copolymers can beselected from the group consisting of syndiotactic and isotacticpolystyrenes. Respective structural characteristics defined in theenclosed claims can be considered by suitable methods and means,structural changes, selection of suitable components of the co(polymers)and so on.

A polymer or copolymer particularly preferable for the selectivesintering process according to the invention has at least one of thefollowing structural characteristics and/or modifications:

-   -   (i) at least one branching group in the backbone chain of the        polymer or copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the branching group is an aromatic        structural unit in the backbone chain of the polymer or        copolymer;    -   (ii) modification of at least one end group of the backbone        chain of the polymer or copolymer;    -   (iii) at least one bulky group in the backbone chain of the        polymer of copolymer, provided that in case of the use of        polyaryletherketones (PAEK) the bulky group is not selected from        the group consisting of phenylene, biphenylene, naphthalene and        CH₂— or isopropylidene-linked aromatics;    -   (iv) at least one aromatic group non-linearly linking the        backbone chain.

The structural modifications (i) to (iv) are explained in the following.

By the structural characteristic (i) “branching group”, a group G is tobe meant having, besides of the bonds linking the portions of thebackbone chain of the polymer (portions A and B of the backbone chain),as shown below

portion A of backbone chain

portion B of backbone chain,at least one side chain and substituent S respectively. Advantageously,G is an aliphatic hydrocarbon, an aromatic hydrocarbon or a heteroarene.The side chains or the substituents “S” respectively affect the mobilityof the polymer chain in the melt and thus enable to suitably influencethe final crystallinity of the manufactured object. Preferably, thesubstituents are independently from each other selected from the groupconsisting of C1 to C6 unbranched or branched, chain- or ringshapedalkyl or alkoxy groups and aryl groups, wherein methyl, isopropyl,tert-butyl or phenyl are particularly preferred. Furthermore, sidechains or substituents S are preferred which respectively allow furtherderivatizations of the obtained polymers or copolymers—optionally afterdeprotection—, for example the synthesis of graft copolymers. The aboveexemplary illustration of the branching group merely shows one branchinggroup. However, more branching groups may exist in the polymer, inparticular in case the branching group is a part of the repeating unitof the polymer. The structural unit (G-S) also may be single or multiplecomponent of the above shown portions A and/or B of the backbone chain.In case of the use of polyaryletherketones (PAEK), the branching groupis an aromatic structural unit in the backbone chain of the polymer orcopolymer.

By the structural characteristic (ii) “modification of at least oneterminal group of the backbone chain of the polymer or copolymer” thereis to be meant, as shown below, the derivatisation of one end or bothends X and Y of the backbone chain of the polymer by

backbone chain of the polymer

backbone chain of the polymer

means of the terminal groups R₁ and/or R₂, wherein n, m areindependently from each other 0 or an integer number, preferably 1,wherein both n, m are not concurrently 0. As denoted by n, m, multiplemodifications of terminal groups may exist. In this embodiment it isrelevant that respectively unmodified terminal groups X and Y may serveas seed crystal and hence may stimulate an undesired excessivecrystallisation. Therefore, at least one of the terminal groups X and Yof the polymer of copolymer can be derivatised in order to interferewith crystallisation and in this way limiting the crystallinity of themanufactured object. Preferably, the terminal groups R₁ and R₂ areindependently selected from alkyl-, alkoxy-, ester- and/or aryl groups.For example, R₁ and R₂ are independently from each other selected fromthe group consisting of branched or non-branched C1-C6 alkyl groups,preferably methyl, isopropyl or tert-butyl; branched or non-branchedC1-C6 alkoxy groups, preferably methoxy, isopropyloxy, t-butyloxy;substituted or unsubstituted C1-C6 aliphatic ester groups, preferablymethyl ester, ethyl ester, isopropyl ester or tert-butyl ester;substituted or unsubstituted aromatic ester groups, preferably benzoicester and substituted or unsubstituted aryl groups, preferably phenyl,naphthyl, anthracenyl. The terminal groups may also be selected suchthat they result in a chain extension by a chemical reaction with eachother at temperatures preferably above T_(m) of the polymer, for examplepolycondensation, electrophilic or nucleophilic substitution, orcoupling reaction. This in turn brings about that the finalcrystallinity within the object decreases by an increased molar mass.

By the structural characteristic (iii) “bulky groups”, for examplecycloalkyls like cyclohexyl or polycyclic cycloalkyls like decalines ornorbornanes which may contain heteroatoms within their ring structureare meant. Further examples for bulky groups are aromatics likephenylene or condensed polycyclic aromatics or heteroaromates, forexample naphthalene or anthracene, fluorene and fluorene derivatives, orpolynuclear aromatic hydrocarbons like biphenylene or terphenylene. Thebulky groups represent rigid rod segments within the polymer chain, thuscan interfere with crystallisation and contribute to a lower finalcrystallinity within the manufactured object. The selection of the bulkygroup depends on the type of polymer or copolymer. While for example incase of an aliphatic polymer such as polyethylene already one phenyleneunit may represent a bulky group, phenylene can not be regarded as abulky group in case of a polyaryletherketone which by definitioncontains phenylene units. In case of the use of polyaryletherketones(PAEK), for the embodiment according to structural characteristic iii),the bulky group is not selected from the group consisting of phenylene,biphenylene, naphthalene and CH₂— or isopropylidene-linking aromatics.

By the structural characteristic (iv) “non-linearly linking aromaticgroups”, aromatic groups are meant which link portions of the backbonechain such that they are positioned non-linearly to each other, that is,the angle between the portions of the backbone chain is different from180°.

By the incorporation of non-linearly linking aromatic groups in thebackbone chain of a polymer, the final crystallinity in the manufacturedobject can be decreased in a controlled way, whereby advantageousmechanical properties like Young's modulus, tensile strength andelongation at break are obtained. In addition, the melting point of thepolymer can be decreased by the incorporation of non-linear linkingaromatic groups such that it is within a particularly advantageoustemperature range, and the glass temperature can be set such that themanufactured object has a particularly advantageous heat distortiontemperature.

Non-linearly linking aromatic groups are, for example, 1,3-phenylene and1,2-phenylene, since they link together the portions A and B of thebackbone chain of the polymer as shown below

at an angle of 120° and 60°, respectively. Further preferred non-lineararomatic groups are for example 1,3-xylylene, 2,4′ and 3,4′-biphenyleneas well as 2,3- and 2,7-naphthalene.

In contrast to a non-linearly linking group, a linearly linking aromaticgroup links the portions of the backbone chain at an angle of 180°. Forexample, 1,4-phenylene represents a linearly linking aromatic group,since the schematically depicted portions A and B of the backbone chainof the polymer are linked at an angle of 180°, as shown below.

A linearly linking group consisting of a condensed aromatic can linearlylink the portions of the backbone chain in two different ways, which isexemplary elucidated by means of naphthalene, but which is also validfor other condensed aromatics such as e.g. anthracene or phenanthrene.For example, naphthalene in the form of 1,4-naphthalene can link theportions A and B of the backbone chain of the polymer together at anangle of 180°. Alternatively, naphthalene can also linearly link in theform of 1,5-naphthalene or 2,6-naphthalene, wherein the schematicallydepicted portions A and B of the backbone chain are then arrangedparallel to each other.

1,5-naphthalene as linearly linking unit:

2,6-naphthalene as linearly linking unit:

The above exemplary figures for the respectively non-linearly andlinearly, linking aromatic group merely show one respectivelynon-linearly and linearly linking aromatic group. However, morerespectively non-linearly and linearly linking groups may be present inthe polymer, in particular if the non-linearly or linearly linking groupis a component of the repeating unit of the polymer.

According to structural characteristic (iv), combinations ofnon-linearly linking aromatic groups and linearly linking aromaticgroups are possible.

Furthermore, a suitably set molecular weight of the polymer contained inthe powder can contribute to a significant decrease of the crystallinityin the manufactured object, which in turn results in a significantimprovement of certain, very advantageous mechanical properties in themanufactured object. Thus, the molecular weight M_(n) (average number)is preferably set to at least 10.000, more preferably 15.000 to 200.000and in particular 15.000 to 100.000, or M_(w) (weight average) ispreferably set to at least 20.000, and more preferably 30.000 to500.000, and in particular 30.000 to 200.000.

Analogous explanations as stated above for the molecular weight alsoapply for the melting viscosity of the polymer or copolymer. The meltingviscosity correlates with the molecular weight of the polymer orcopolymer as follows: the higher the molecular weight of a polymer orcopolymer, the higher is its melting viscosity. Therefore, the preferredmelting viscosities e.g. of polyaryletherketones and their copolymers ingeneral are in a range of 0.05-1.0 kN*s/m², preferably 0.15-0.6 kN*s/m²and in particular 0.2-0.45 kN*s/m². The melting viscosity can bedetermined in a capillary viscometer at 400° C. and at a shearing rateof 1000 s⁻¹ according to an instruction of US-Patent 2006/0251878 A1.

The polymers or copolymers can be admixed with an alloying component ina mixture (blend), wherein a blend of at least two different polymers orcopolymers is used. In such blends, it is preferred that at least onecomponent of the blend decreases the final crystallinity of themanufactured object.

For the desired result, in particular the crystallinity within themanufactured object as well as its mechanical properties, beyond thegeneral conditions for the structural characteristics (i) and (iii)comprised in the polymer or copolymer, for polyaryletherketones (PAEK)the following limitations apply:

-   -   for feature (i): the branching group is an aromatic structural        unit in the backbone chain of the polymer or copolymer, and    -   for feature (iii): the bulky group is not selected from the        group consisting of phenylene, biphenylene, naphthalene and CH₂—        or isopropylidene-linked aromatics.

For other types of polymers, in particular polyamides (PA), polyesters,polyethers, polyolefines, polystyrenes, polyphenylensulfides,polyvinylidenfluorides, polyphenylenoxides, polyimides or a copolymercomprising at least one of the aforementioned polymers, the limitationsmade for polyaryletherketones do not apply for.

In the following, some significant structural properties ormodifications of a polymer- or copolymer material are exemplarydescribed by means of PAEK polymers and -copolymers which are suitablefor a preselection applicable to a selective sintering process by meansof electromagnetic radiation. It is obvious for a person skilled in theart that the below described structural properties or modifications canlikewise be applied to other types of polymers or copolymers.

The formula shown below shows a general structure of PAEK or PAESpolymers and copolymers that are preferred to manufacture laser sinteredobjects, wherein structural peculiarities preferred alone or incombination in order to obtain low crystallinities, will be furtherdescribed below:

Ar₁, Ar₂ and Ar₃ are linearly or non-linearly linking, unsubstituted orsubstituted, monocyclic or polycyclic aromatic hydrocarbons, whereinindependent from Rf₁, Rf₂ and/or Rf₃ being H, substituents can beoptionally selected from:Rf₁, Rf₂, Rf₃ independently from each other are selected from the groupconsisting of C1-C6 straight chain, branched or cyclic alkyl and alkoxygroups, and aryl groups, preferably Me, i-Pr, t-Bu, Ph (forunsubstituted Ar₁, Ar₂ and Ar₃, Rf₁, Rf₂, Rf₃=H), wherein each Ar₁, Ar₂and Ar₃ may have one or more substituent(s) Rf₁, Rf₂, Rf₃ respectively,X=O and/or SY=CO and/or SO₂Z=SO₂, CO, O and/or Sa is a low integer which is more than 0, preferably lower than 12, morepreferably 1 to 6 and in particular 1 to 3,b is a low integer which is more than 0, and preferably lower than 12,more preferably 1 to 6 and in particular 1 to 3,c is 0 or a low integer, preferably lower than 12, more preferably 1 to6 and in particular 1 to 3,n denotes the degree of polymerisation.

In the above general formula, the indices a, b and c denote the numberof the respective units in the repeating unit of the polymer or therepeating units of the copolymer respectively, wherein one or moreunit(s) of the same kind, e.g. the unit indexed with a, may be locatedbetween units of a different kind, e.g. the unit indexed with b and/orc. The location of the respective units in the repeating unit may bederived from the abbreviation of the PAEK derivative.

The above general formula for PAEK- or PAES polymers or

-copolymers shall be clarified by means of the following examples of aPAEK polymer according to the invention. Thus, in one embodiment ofusing PAEK according to the invention, Ar₁ is unsubstituted4,4″-p-terphenylene, X=O and a=1, Ar₂ is unsubstituted 1,4-phenylene, Yis O and b=1 and Ar₃ is unsubstituted 1,4-phenylene, z is CO and c=1,wherein following structural formula results for this PAEK

, wherein n denotes the degree of polymerisation.

In PAEK polymers or copolymers, besides the conventional 1,4 phenylene,groups being more bulky as those selected from the group consisting ofbiphenylenes, naphthalenes and CH₂— or isopropylidene-linked aromaticsshall be selected, like p-terphenylene.

The following two examples for the PAEK polymers PEKK and PEKEKK areexamples for PAEK polymers having linearly linking aromatic groups.Thus, for example, for PEKK, Ar₁ is an unsubstitued 1,4-phenylene, X isO and a=1, Ar₂ is an unsubstituted 1,4-phenylene, Y is CO and b=2 andc=0, wherein the following structural formula results for PEKK

, wherein n denotes the degree of polymerisation. In the further examplePEKEKK, Ar₁ is unsubstituted 1,4-phenylene, X is O and a=2, Ar₂ isunsubstituted 1,4-phenylene, Y is CO and b=3 and c=0, wherein thefollowing structural formula results for PEKEKK

, wherein n denotes the degree of polymerisation.

The following example shows a PAEK polymer applied according to theinvention, namely a PEKK copolymer having non-linearly linking units.This PEKK copolymer has 2 different repeating units (cf. repeating unitA and B in the below structural formula).

repeating unit A:

repeating unit B:

In the repeating unit A, Ar₁ is unsubstituted 1,4-phenylene, X is O anda=1, Ar₂ is unsubstituted 1,4-phenylene, Y is CO, b=2 and c=0. In therepeating unit B, Ar₁ is unsubstituted 1,4-phenylene, X is O and a=1,Ar₂ is unsubstituted 1,3-phenylene, Y is CO and b=1 and Ar₃ is1,4-phenylene, Z is CO and c is 1. Depending on the synthesis, therepeating units A and B may be arranged strictly alternating,statistically or blockwise in the backbone chain of the copolymer. Thedegree of polymerisation n of this PEKK copolymer results from the sumof n₁ and n₂.

In selective sintering of the above described PEKK copolymers it wassurprisingly found that the final crystallinity of the manufacturedobject is the lower, the higher the content of 1,3-phenylene units is(compare Example 1 with Example 2). Furthermore it was found that themelting point of the copolymer can be lowered by increasing the contentof 1,3-phenylene units in the PEKK copolymer. Such a lowering of themelting point is an advantage for the procedural processing in lasersintering. Thereby, a lower temperature of the process chamber can beselected, which enables an energy efficient sintering process.Therefore, the ratio of 1,4-phenylene units Ar₂ in the repeating unit Ato 1,3 phenylene units Ar₂ in the repeating unit B is preferably90/10-10/90, more preferably 70/30-10/90 and in particular 60/40-10/90.Such PEKK copolymers can for example be obtained by electrophilicaromatic substitution of diphenylether as well as terephthalic-acid and-acid chloride, respectively, as the monomer having 1,4-phenylene unitsand isophthalic-acid and -acid chloride, respectively, as the monomerhaving 1,3-phenylene units.

Moreover, the ratio between the number of ketone groups Y and the numberof ether- or thioether groups is preferably 1:4 to 4:1. Within thisrange, the final crystallinity in the manufactured object can besignificantly reduced.

The larger the required space of the aromatic hydrocarbons Ar₁, Ar₂ andAr₃, the more the aromatic hydrocarbons behave like a rigid rod segment,and the lower is the final crystallinity of the manufactured object.Hence, it is preferred that the aromatic hydrocarbon groups Ar₁, Ar₂ andAr₃ are respectively and independently selected from the groupconsisting of 1,4-phenylene, 4,4′-biphenylene,4,4′-isopropylidendiphenylene, 4,4′-diphenylsulfone, 1,4-, 1,5- and2,6-naphthalene, 4,4″-p-terphenylene and 2,2-bis-(4-phenylen)-propanefor linearly linking aromatic groups, and for non-linearly linkingaromatic groups, they are respectively and independently selected fromthe group consisting of 1,2- and 1,3-phenylene, 1,3-xylylene, 2,4′- and3,4′-biphenylene and 2,3- and 2,7-naphthalene.

In case of polyaryletherketones, branching groups can be provided byaromatic hydrocarbons Ar₁, Ar₂ and Ar₃ having substituents Rf₁, Rf₂,Rf₃, wherein in this case it is not relevant whether the linkage at thearomatic is linear or non-linear.

A further possibility for tailoring the polymer such that lowcrystallinities in the manufactured object are achieved after theselective sintering process is the use of a suitable copolymer. ForPAEK, besides of the above mentioned PEKK copolymers, copolymers withpolyarylethersulfone (PAES) are preferred, in particular preferablypolyaryletherketone(PAEK)/polyarylethersulfone(PAES)-diblock copolymersor PAEK/PAES/PAEK-triblock copolymers, more preferably polyetherketone(PEK)/polyethersulfone (PES)-diblock copolymers or PEK/PES/PEK-triblockcopolymers. It was found that the crystallinity of the manufacturedobject is the lower the higher the amount of thepolyarylethersulfone-component is. Thus, the ratio of the number ofsulfone groups Z to the number of keto groups Y is preferably between50:50 and 10:90. Within this ratio range, a glass transition temperature(T_(g)) and a melting point (T_(m)) of the polymer material can beadjusted which is suitable for processing the polymer in an apparatusfor manufacturing a three-dimensional object by a selective sintering bymeans of electromagnetic radiation. In order to provide a suitableprocessing temperature for the selective sintering process, said PEK/PEScopolymers preferably have a T_(g) higher than 180° C. and a meltingtemperature T_(m) of 300 to 430° C.

The end groups of the backbone chain of the polymer or copolymer dependon the kinds of monomers used for synthesis and on the kind ofpolymerisation. In the following, two different kinds of PAEK synthesisschemes resulting in different kinds of PAEKs with different end groupsare shown.

PAEKs can be normally synthesized in two ways, namely by electrophilicaromatic substitution (Friedel-Crafts-Acylation) or nucleophilicaromatic substitution. For example, in the nucleophilic synthesis of aPAEK, a 1,4-bishydroxy-benzene is polymerized with an 4,4′ dihalogenatedbenzophenone component:

xHO-Ph-OH+(y+1)Hal-Ph-CO-Ph-Hal→Hal-Ph-CO-Ph-[O-Ph-O]_(x)[Ph-CO-Ph]_(y)-Hal

, wherein Hal is F, Cl, Br and x and y denote the number of monomersincorporated in the polymer.

As a result, the PAEK backbone chain, in the above example PEEK may beterminated with a residual halogen group after the polymerization, mostsuitably with fluorine, optionally alternatively with chlorine orbromine, at none or one end (not shown) or at both ends (shown) of thebackbone chain. The same applies for the synthesis of PAEK orpolyethersulfone (PAES) copolymers, wherein the dihalogenated ketoneunit may be substituted partly by a dihalogenated aromatic sulfone. Thearomatic bishydroxy-component may likewise be partly or fullysubstituted by a bisthiol component.

For example, the halogen substituted ends of the polymer may bederivatized by a termination reaction with phenol:

2Ph-OH+Hal-Ph-CO-Ph-[O-Ph-O]_(x)[Ph-CO-Ph]_(y)-Hal→Ph-O-Ph-CO-Ph-[O-Ph-O]_(x)[Ph-CO-Ph]_(y)-O-Ph

Preferably, Hal in the formulae above is F.

The same applies for the synthesis of PAEK- or polyethersulfone(PAES)copolymers, wherein the dihaloginated ketone unit is partly replaced bya dihaloginated aromatic sulfone unit. The aromatic bishydroxy componentcan be replaced partly or totally by a bisthiol component, too.

In the case of synthesis of PAEK polymers or copolymers by electrophilicaromatic substitution reaction, diacylaromates, e.g. aromatic diacids orpreferably aromatic diacid chlorides or aromatic diacid anhydrides, arepolymerized with a bisaromatic ether or thioether component. Forexample, for PEKK, this may result in PEKK polymers or copolymers withphenyl groups at none or one end (not shown) or both ends (shown) of thebackbone chain:

xR_(A)OC-Ph-COR_(A)+(y+1)Ph-O-Ph→Ph-O-Ph-[OC-Ph-CO]_(x)[Ph-O-Ph]_(y)-H

, wherein R_(A) is Cl or —OH and x and y denote the number of monomersincorporated in the polymer.

Alternatively, a synthesis by a single monomer route using, for example,an aromatic mono-acid chloride may be applied.

For example, the phenyl groups at the ends of the polymer may bederivatized by a termination reaction with benzoic acid chloride:

2Ph-COCl+Ph-O-Ph-[OC-Ph-CO]_(x)[Ph-O-Ph]_(y)-H→Ph-CO-Ph-O-Ph-[OC-Ph-CO]_(x)[Ph-O-Ph]_(y)-OC-Ph

Irrespective if a nucleophilic or aromatic substitution reaction ischosen, to slow down crystallization of the polymer, the end groups maybe preferably substituted, e.g. such that a PAEK polymer has thefollowing formula:

R_(T)—U-[PAEK]—U—R_(T)

, wherein U is a linking moiety, for example NH, O, CO, CO—O—, SO, asingle bond, —(CH₂)_(k) wherein k is 1-6, or the like; and the left handand right hand structural moieties R_(T) may be the same or differentstructural groups, usually the structural moieties R_(T) are the same.

Preferably, R_(T) is selected from the group of unsubstituted orsubstituted aliphatic or aromatic hydrocarbon residues. U may be formedby direct reaction with the ends of the polymer or copolymer, forexample a monofunctional hydroxy compound may form O as U, or it may beintroduced as a substituent of the termination reagent, e.g.HO-Ph-COO-tert-butyl may form COO as U.

Furthermore, if it is necessary to increase the crystallization rate inorder to adjust the crystallinity of the manufactured three-dimensionalobject appropriately, the polyaryletherketones with a halogenated endgroup can be terminated with ionic end groups like e.g. phenate saltslike NaOPhSO₃Na or NaOPhCOPhOPhSO₃Na. Subsequent acidification of thephenate salts with e.g. HCl leads to —SO₃H end groups that show aslightly reduced nucleation effect.

Furthermore, in the following—again exemplary—now by means of PApolymers and -copolymers, further significant structural characteristicsor modifications of a polymer- or copolymer-material are described,which are suitable for a preselection applicable to selective sinteringprocess by means of electromagnetic radiation. For the person skilled inthe art, it is apparent that the below described structuralcharacteristics or modifications can in turn be applied to other typesof polymers, too.

The formula below shows a general structure of partly aromatic PApolymers and -copolymers, which is preferred to manufacture lasersintered objects, wherein structural peculiarities necessary forobtaining low crystallinities are further described hereinafter:

K, L=C2-C20 linear chain or cyclic alkyl groups, unsubstituted orsubstituted,Ar₄ and Ar₅ are linearly or non-linearly linking, unsubstituted orsubstituted, monocyclic or polycyclic aromatic hydrocarbons, wherein,independent from Rf₄, Rf₅, Rf₆ and/or Rf₇ being H, substituents can beoptionally chosen from:Rf₄, Rf₅, Rf₆, Rf₇ are independently from each other selected from thegroup consisting of C1-C6 linear chain, branched or cyclic alkyl- andalkoxy groups, and aryl groups, preferably selected from Me, i-Pr, t-Bu,Ph, wherein each of K, L, Ar₄ and Ar₅ respectively has one or moresubstituents Rf₄, Rf₅, Rf₆, Rf₇ (for unsubstituted K, L, Ar₄ and Ar₅,then Rf₄, Rf₅, Rf₆, Rf₇=H),

T, U, V, W=—NH—CO— or —CO—NH—,

d is a low integer number being more than 0 and preferably lower than12, more preferably 1 to 6 and in particular 1 to 3,e, f and g are 0 or a low integer number, preferably lower than 12, morepreferably 1 to 6 and in particular 1 to 3,n denotes the degree of polymerisation.

In the above general formula, the indices d, e, f and g denote thenumber of the respective repeating units of the polymer and in therespective repeating units of the copolymer, respectively, wherein oneor more unit(s) of the same kind, e.g. the unit indexed with d, may belocated between the units of another kind, e.g. the unit indexed with e,f and/or g.

The following example for a polyamide polymer used according to theinvention shall clarify the above general formula for polyamidepolymers.

The PA6-3-T polyamide polymer used according to the invention hasfollowing repeating units:

repeating unit A:

repeating unit B:

In repeating unit A, K is a n-hexane chain disubstituted in 2-positionand monosubstituted in 4-position with Rf₄=methyl, T is —NH—CO— and d=1,e=0, Ar₄ is unsubstituted 1,4-phenylene, V is —CO—NH— and f=1 and g=O.Since there are 2 possibilities for the substituted hexane diamine toreact with terephthalic acid, this results in a second repeating unit B.In repeating unit B, K is a n-hexane chain disubstituted in 2-positionand monosubstituted in 4-position with Rf₄=methyl, T is —NH—CO— and d=1,e=0, Ar₄ is unsubstituted 1,4-phenylene, V is —CO—NH— and f=1 and g=0.

The following two examples for polyamide polymers PA 6T/6I and PA MXD6applied according to the invention are examples for polyamide polymershaving non-linearly linking aromatic groups.

The polyamide PA 6T/6I copolymer has 2 different repeating units (cf.repeating unit A and B in the below structural formula).

repeating unit A:

repeating unit B:

In the repeating unit A, K is an unsubstituted n-hexane chain, T is—NH—CO— and d=1, e=0, Ar₄ is unsubstituted 1,4-phenylene, V is —CO—NH—and f=1 and g=0. In the repeating unit B, K is an unsubstituted n-hexanechain, T is —NH—CO— and d=1, e=0, Ar₄ is unsubstituted 1,3-phenylene, Vis —CO—NH— and f=1 and g=0. The degree of polymerisation n of this PAcopolymer results from the sum of n₁ and n₂.

The following example shows a further polyamide applied according to theinvention, namely poly-m-xylylene adipamide (polyamide MXD6) havingnon-linearly linking units in the backbone chain. According to the abovegeneral formula, for polyamide MXD6, K is an unsubstituted n-butanechain, T is

—CO—NH— and d=1, e=0, Ar₄ is unsubstituted 1,3-xylylen, V is —NH—CO— andf=1 and g=0, wherein the following structural formula results for MXD6

, wherein n denotes the degree of polymerisation.

In case of polyamides, branching groups can be provided by aliphaticresidues K and L and/or aromatic hydrocarbons Ar₄ and Ar₅ substitutedwith one or more of the substituents Rf₄, Rf₅, Rf₆ and Rf₇.

In case of polyamides, the bulky groups are selected from aromatic ornon-aromatic groups. In particular, structural units selected from thegroup consisting of phenylene, naphthalene, anthracene, biphenyl,fluorenes, terphenyl, decaline or norbornane have to be considered.

In the remainder polymers, analogous considerations apply for the bulkygroups as given for the polyamides.

The structural characteristics explained for PAEK polymers and-copolymers as well as for PA-(co)polymers can also be applied to other,already exemplary mentioned polymer- or copolymer-materials. The skilledperson will appreciate that corresponding structure modifications can bemade with the effect of reducing crystallinity in the producedthree-dimensional object.

Furthermore, the powder may be a composite powder comprising one or morefiller(s) and/or additive(s) besides a matrix of the respective polymer,copolymer or blend. Fillers may be used to further improve themechanical properties of the manufactured object. For example, carbonfibers, glass fibers, Kevlar fibers, carbon nanotubes, or fillers, thefiller preferably having a low aspect ratio (glass beads, aluminum grit,etc.) or mineral fillers such as titan dioxide may be incorporated inthe powder comprising at least one polymer or copolymer. Furthermore,processing additives which improve the processability of the powder,e.g. free flowing agents such as those from the Aerosil series (e.g.Aerosil R974, Aerosil R812, Aerosil 200), or other functional additivessuch as heat stabilizers, oxidation stabilizers, color pigments (carbonblack, graphite, etc.) may be used.

From the findings of the present invention it can be inferred that thefollowing structural characteristics or modifications of polymers orcopolymers provide for a decreased crystallinity in the manufacturedobject and thus are particularly preferred when a preselection ofspecific types of polymer or copolymer is made, e.g. amongpolyaryletherketones (PAEK), polyarylethersulfones (PAES), polyamides,polyesters, polyethers, polyolefines, polystyrenes,polyphenylensulfides, polyvinylidenfluorides, polyphenylenoxides,polyimides and copolymers comprising at least one of the aforementionedpolymers:

-   -   a) Preselection of a polymer or copolymer having at least one of        the following structural characteristics and/or modifications:        -   (i) at least one branching group within the backbone chain            of the polymer or copolymer, provided that in the case of            the use of polyaryletherketones (PAEK) the branching group            is an aromatic structural unit in the backbone chain of the            polymer or copolymer;        -   (ii) modifying at least one terminal group of the backbone            chain of the polymer or copolymer;        -   (iii) at least one bulky group in the backbone chain of the            polymer or copolymer, provided that in the case of the use            of polyaryletherketones (PAEK) the bulky group is not            selected from the group consisting of phenylene,            biphenylene, naphthalene and CH₂— or isopropylidene-linked            aromatics;        -   (iv) at least one aromatic group non-linearly linking the            backbone chain,    -   b) using relatively high molecular masses M_(n) or M_(n) or        certain melt viscosities,    -   c) using long chain lengths or high degrees of polymerisation,    -   d) mixing or blending by admixing of at least two different        polymers or copolymers.

The following examples are merely illustrative of the present inventionand they should not be considered as limiting the scope of the inventionin any way. The examples and modifications or other equivalents thereofwill become apparent to those versed in the art in the light of thepresent entire disclosure.

EXAMPLES

The density of the manufactured three-dimensional object was measuredaccording to ISO 1183 on a Kern 770-60 balance with a Satorius densitydetermination set YDK 01. The porosity of the object can be determinedvia the density in case the theoretical density of 100% crystallinepolymer, the theoretical density of amorphous polymer and thecrystallinity of the manufactured polymeric object are known. Thecrystallinity in the manufactured object can be measured by means ofdynamic differential calorimetry (DCC or DSC) according to DIN 53765.

Alternatively, the crystallinity can be determined via Wide Angle X-rayScattering (WAXS) measurements. The procedure is known by the personskilled in the art. If the theoretical density values for the polymerare not known, the porosity can also be determined bymicro-computerthomography measurements. A suitable device is e.g. theμ-CT40 supplied by SCANCO Medical AG, Brüttisellen, Switzerland. Theprocedure is known by the person skilled in the art.

The following examples are merely for illustration and should not beconsidered as limitative.

Reference Example

A powder manufactured from structurally unmodified PEEK (purchased fromthe company Victrex Plc, Thornton Cleveleys, Lancashire FY5 4QD, GreatBritain) having an average particle size distribution of 48 μm, whereinthe PEEK polymer has a molecular mass of Mn=23,000 and Mw=65,000 and amelt viscosity of 0.15 kN*s/m², is thermally treated above the glasstransition temperature in an oven.

The PEEK powder having a bulk density of 0.45 g/cm3 was processed on alaser sintering machine of the type P700, that was modified by EOScompany for high temperature applications. The temperature of theprocess chamber was 335° C.

After the laser sintering process was finished, the cooling rate wascontrolled by post-heating between 335° C. and Tg of PEEK (145° C.). Thecooling rate showed a maximum average of 0.3° C./min.

The manufactured three-dimensional parts showed the followingproperties:

density=1.316 g/cm³crystallinity (by DSC)=52%porosity (calculated by density/crystallinity)=1.4%Tensile strength test (ASTM D638, Type I):

-   -   Young's modulus=4500 MPa    -   Tensile strength=44 MPa    -   Elongation at break=1.04%

Example 1 (According to the Invention)

A powder producible from a structurally modified PAEK having thestructural formula

, which may have an average particle size distribution of <100 μm, isthermally treated above the glass transition temperature in an oven.

The PAEK powder is processed on a laser sintering machine of the typeP700, that was modified by EOS company for high temperatureapplications. The temperature of the process chamber is for example 10°C. below the melting point of the PAEK powder.

After the laser sinter process is finished, the cooling rate iscontrolled by post-heating between the temperature of the processchamber and Tg of the PAEK such that the cooling rate shows a maximumaverage of 0.3° C./min.

Example 2 (According to the Invention)

A powder producible from a structurally modified PEEK having thestructural formula

, which has an average particle size distribution of 50 μm, wherein thePEEK polymer has a molecular weight of Mn=32,000 and Mw=65,000, isthermally treated above the glass transition temperature in an oven.

The PEEK powder is processed on a laser sintering machine of the typeP700, that was modified by EOS company for high temperatureapplications. The temperature of the process chamber is for example 335°C.

After the laser sinter process is finished, the cooling rate iscontrolled by post-heating between 335° C. and Tg of the PEEK (about145° C.) such that the cooling rate shows a maximum average of 0.3°C./min.

Example 3 (According to the Invention)

A powder producible from Polyamid PA6-3-T having the structural formula

repeating unit A:

repeating unit B:

, which may have an average particle size distribution of <100 μm isthermally treated above the glass transition temperature in an oven.

The polyamide powder is processed on a laser sintering machine of thetype P700, that was modified by EOS company for high temperatureapplications. The temperature of the process chamber is for example 5°C. below the melting point of the polyamide.

After the laser sinter process is finished, the cooling rate iscontrolled by post-heating between the temperature of the processchamber and Tg of the polyamide such that the cooling rate shows amaximum average of 0.3° C./min.

Example 4 (According to the Invention)

A powder producible from structurally modified polyethylene PE-LLD(linear low density) having the structural formula

-   -   R=butyl, hexyl or octyl    -   n, m=integers, such that there is a ratio of 15-30 short chain        branchings per 1000 C-atoms        , which may have an average particle size distribution of <150        μm.

The PE-LLD powder is processed on a laser sintering machine of the typeP390 of the EOS company. The temperature of the process chamber is forexample 5° C. below the melting point of the PE-LLD powder.

After the laser sinter process is finished, the cooling rate of theprocess chamber at 40° C. is controlled such that the cooling rate showsa maximum average of 0.2° C./min.

Example 5 (According to the Invention)

A powder producible from structurally modified polyethylene PE-HD (highdensity) having the structural formula

-   -   R=methyl    -   n, m=integers, such that there is a ratio of 15-30 short chain        branchings per 1000 C-atoms        , which may have an average particle size distribution of <150        μm.

The PE-HD powder is processed on a laser sintering machine of the typeP390 of the EOS company. The temperature of the process chamber is forexample 5° C. below the melting point of the PE-HD powder.

After the laser sinter process is finished, the cooling rate of theprocess chamber at 40° C. is controlled such that the cooling rate showsa maximum average of 0.2° C./min.

Example 6 (According to the Invention)

A thermally treated PEKK powder (type PEKK-C, purchased from the companyOPM, Enfield, Conn., USA) with a ratio of repeating units respectivelycontaining at least one 1,4-phenylene unit to repeating units containingrespectively at least one 1,3-phenylene unit, of 80:20, a melting pointof 367° C. as well as a mean particle size d₅₀=55 μm was processed on alaser sintering machine of the type P700 that was modified by EOS forhigh temperature applications. The temperature of the process chamberwas 343° C. The cooling rate showed a maximum average of 0.3 K/min.

The laser-sintered parts averagely had the following properties:

density: 1.246 g/cm³tensile strength (ISO 527-2):

Young's modulus: 4200 MPa tensile strength:  39 MPa elongation at break:1.0%

Example 7 (According to the Invention)

A thermally treated PEKK powder (Typ PEKK-SP, purchased from the companyOPM, Enfield, Conn., USA) with a ratio of repeating units, respectivelycontaining at least one 1,4-phenylene unit to repeating unitsrespectively containing at least one 1,3-phenylene unit of 60:40, amelting point of 297° C. as well as a mean particle size d₅₀=60 μm wasprocessed on a laser sintering machine of the type P700 that wasmodified by EOS for high temperature applications. The temperature ofthe process chamber was 286° C. The average cooling rate between286-250° C. was higher than 0.3 K/min. Between 250° C. and T_(g), it wasdefined by the natural heat loss.

The laser-sintered parts averagely had the following properties:

density: 1.285 g/cm³tensile strength (ISO 527-2):

Young's modulus: 3900 MPa tensile strength:  69 MPa elongation at break:1.9%

1. A process for manufacturing a three-dimensional object from a powderby selective sintering by means of electromagnetic radiation, whereinthe powder comprises a polymer or copolymer which has at least one ofthe following structural characteristics: (i) at least one branchinggroup in the backbone chain of the polymer or copolymer, provided thatin case of the use of polyaryletherketones (PAEK) the branching group isan aromatic structural unit in the backbone chain of the polymer orcopolymer; (ii) modification of at least one end group of the backbonechain of the polymer or copolymer; (iii) at least one bulky group in thebackbone chain of the polymer of copolymer, provided that in case of theuse of polyaryletherketones (PAEK) the bulky) group is not selected fromthe group consisting of phenylene, biphenylene, naphthalene and CH₂— orisopropylidene-linked aromatics; (iv) at least one aromatic groupnon-linearly linking the backbone chain.
 2. The process according toclaim 1, wherein successive layers of the object to be formed fromsolidifiable powder material are subsequently solidified at positionscorresponding to the cross section of the object; and/or in whichprocess the electromagnetic radiation is provided by a laser.
 3. Theprocess according to claim 1 or 2, which comprises a predefined and/orcontrolled cooling step after the sintering step, wherein preferably thestep of cooling is applied to the object after completion of the objectfrom a temperature being 1-50° C. lower than T_(m) of the polymer orcopolymer comprised in the powder, to T_(G) of the polymer or copolymercomprised in the powder, at a cooling rate of 0.01-10° C./min whereinT_(m) is the melting point and T_(G) is the glass transition temperatureof the polymer or the copolymer comprised in the powder.
 4. The processaccording to any one of the preceding claims, wherein the powdercomprises a polymer or copolymer having at least one of thecharacteristics selected from the group of: a melting point T_(m) in arange of 100° C. to 450° C.; a glass transition temperature T_(G) in arange of 50 to 300° C.; a number average M_(n) of at least 10,000 or aweight average M_(w) of at least 20,000; and a polymerization degree nof 10 to 10,000.
 5. The process according to any one of the precedingclaims, wherein the polymer or copolymer contains at least one aromaticgroup having at least one of characteristics selected from the group of:the aromatic group is in the repeating unit of the backbone chain; andthe aromatic group is independently from each other selected fromunsubstituted or substituted, monocyclic or polycyclic aromatichydrocarbons, preferably the aromatic group is independently from eachother selected from the group consisting of 1,4-phenylene,4,4′-biphenylene, 4,4′-isopropylidene diphenylene, 4,4′-diphenylsulfone,1,4-, 1,5-, 2,6-naphtalene, 4,4″-p-terphenylene.
 6. The processaccording to any one of the preceding claims, wherein according tomodification (iv) the non-linear linking aromatic group has at least oneof characteristics selected from the group of: at least one non-linearlinking aromatic group is contained in the repeating unit of thebackbone chain, preferably said non-linear linking aromatic group(s)is/are selected from the group of 1,2- and 1,3-phenylene, 1,3-xylylene,2,4′- and 3,4′-biphenylene, and 2,3- and 2,7-naphthalene; and thepolymer or copolymer contains at least one additional, linear-linkingaromatic group which is different from the non-linearly linking aromaticgroup and/or at least one branching group, in the backbone chain,preferably in the repeating unit of the backbone chain, preferably saidlinear-linking aromatic groups are independently from each otherselected from the group consisting of 1,4-phenylene, 4,4′-biphenylene,4,4′-isopropylidene diphenylene, 4,4′-diphenylsulfone, 1,4-, 1,5-,2,6-naphtalene, 4,4″-p-terphenylene and 2,2-bis-(4-phenylen)-propane. 7.The process according to any one of the preceding claims, whereinaccording to modification (i) the branching group is an aliphatichydrocarbon, an aromatic hydrocarbon or a heteroarene which has at leastone substituent or one side chain, in case of the use ofpolyaryletherketones (PAEK), the branching group is an aromaticstructural unit in the backbone chain of the polymer or copolymer,preferably said side chains are independently from each other selectedfrom the group consisting of C1 to C6 unbranched or branched, chain- orringshaped alkyl- or alkoxy groups and aryl groups, more preferably saidside chains are independently from each other selected from the groupconsisting of methyl, isopropyl, tert-butyl or phenyl.
 8. The processaccording to any one of the preceding claims, wherein according tomodification (ii) the end groups of the backbone chain are modified byterminal alkyl, alkoxy, ester and/or aryl groups.
 9. The processaccording to any one of the preceding claims, wherein according tomodification (iii) the bulky group is an aromatic or non-aromatic group,in case of the use of polyaryletherketones (PAEK), the bulky group isnot selected from the group consisting of phenylene, biphenylene,naphthalene and CH₂— or isopropylidene-linked aromatics, preferably thebulky group is a polycyclic aromatic or non-aromatic group, morepreferably the bulky group is selected from phenylene, naphthalene,anthracene, biphenyl, fluorenes, terphenyl, decaline or norbornane. 10.The process according to any one of the preceding claims, wherein thepolymer or copolymer is formed on the basis of polyamide (PA),polyaryletherketone (PAEK), polyarylethersulfone (PAES), polyester,polyether, polyolefines, polystyrene, polyphenylenesulfide,polyvinylidenefluoride, polyphenyleneoxide, polyimide or a blockcopolymer that comprises at least one of the aforementioned polymers,preferably the polymer or copolymer is formed on the basis of polyamide(PA), polyaryletherketone (PAEK), polyarylethersulfone (PAES) or a blockcopolymer comprising at least one of the aforementioned polymers,wherein said block copolymer is preferably a polyaryletherketone(PAEK)/polyarylethersulfone (PAES)-diblock copolymer or aPAEK/PAES/PAEK-triblock copolymer.
 11. The process according to any oneof the preceding claims, wherein the polymer is a polyaryletherketone(PAEK) formed on the basis of polyetheretherketone (PEEK),polyetherketoneketone (PEKK), polyetherketone (PEK),polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone(PEKEKK), polyaryletheretheretherketone (PEEEK) or a copolymercomprising at least one of the aforementioned polymers, preferably apolymer or copolymer on the basis of polyaryletherketone (PAEK) having amelting viscosity of 0.05-1.0 kN*s/m² and/or a polymerization degree nof preferably 10 to 1,000.
 12. The process according to claim 11,wherein the polyetherketoneketone (PEKK) polymer or copolymer comprises1,4-phenylene as the linear-linking aromatic group and 1,3-phenylene asthe non-linear linking aromatic group in the backbone chain of thepolymer, preferably in the repeating unit of the backbone chain;preferably said ratio of repeating units comprising, respectively, atleast one 1,4-phenylene unit to repeating units comprising,respectively, one 1,3-phenylene unit is 90/10-10/90, preferably70/30-10/90, more preferably 60/40 to 10/90.
 13. A three-dimensionalobject obtained by a selective sintering of a polymer, a copolymer or ablend of polymers in powder form by means of electromagnetic radiation,wherein the polymer or copolymer used for the powder has at least one ofthe following structural characteristics: (i) at least one branchinggroup in the backbone chain of the polymer or copolymer, provided thatin case of the use of polyaryletherketones (PAEK) the branching group isan aromatic structural unit in the backbone chain of the polymer orcopolymer; (ii) modification of at least one end group of the backbonechain of the polymer or copolymer; (iii) at least one bulky group in thebackbone chain of the polymer of copolymer, provided that in case of theuse of polyaryletherketones (PAEK) the bulky group is not selected fromthe group consisting of phenylene, biphenylene, naphthalene and CH₂— orisopropylidene-linked aromatics; (iv) at least one aromatic groupnon-linearly linking the backbone chain.
 14. The three-dimensionalobject according to claim 13, wherein the polymer or copolymer isdefined as denoted in the claims 4 to
 12. 15. An apparatus formanufacturing a three-dimensional object from a powder by selectivesintering by means of electromagnetic radiation of the powder, whereinsaid apparatus comprises a temperature control device arranged forsetting a predefined cooling of the object after completion ofmanufacturing the object.
 16. The apparatus according to claim 15,wherein the cooling rate set by means of the temperature control devicedepends on the type of polymer, copolymer or polymer blend comprised inthe powder; and/or wherein the temperature control device is setdepending on the predetermined type of polymer, copolymer or polymerblend.
 17. A manufacturing system including an apparatus according toclaim 15 or 16 and a powder comprising at least one polymer or copolymeras defined in claims 4 to
 12. 18. A use of a polymer powder in themanufacture of a three-dimensional object by means of selectiveelectromagnetic irradiation sintering, wherein the polymer ispreselected from a polymer or copolymer having at least one of thefollowing structural characteristics: (i) at least one branching groupin the backbone chain of the polymer or copolymer, provided that in caseof the use of polyaryletherketones (PAEK) the branching group is anaromatic structural unit in the backbone chain of the polymer orcopolymer; (ii) modification of at least one end group of the backbonechain of the polymer or copolymer; (iii) at least one bulky group in thebackbone chain of the polymer of copolymer, provided that in case of theuse of polyaryletherketones (PAEK) the bulky group is not selected fromthe group consisting of phenylene, biphenylene, naphthalene and CH₂— orisopropylidene-linked aromatics; (iv) at least one aromatic groupnon-linearly linking the backbone chain.
 19. The use according to claim18, wherein the polymer or copolymer is defined as in claims 4 to 12.